Exchange Server 2016 and 2019 End of Life: Next Steps

The Exchange 2019 EOL date was 14 October 2025, the same day Exchange Server 2016 reached end of support. A paid Extended Security Update (ESU) programme bridged the gap, but its final six-month period ends in October 2026 with no further extensions. Your next step is either an upgrade to Exchange Server Subscription Edition (SE) or a move to Exchange Online.

Exchange 2016 and 2019 End of Life Dates at a Glance

The support dates come from Microsoft's lifecycle pages for Exchange Server 2019 and Exchange Server 2016. Microsoft lists the end as 15 October 2025 at 06:59 Pacific Time, which is the end of 14 October in most time zones.

What Does Exchange 2019 EOL Mean for Your Server?

End of life means Microsoft no longer releases security updates, bug fixes or time-zone updates for Exchange 2016 or 2019 unless you pay for ESU. Your server keeps sending and receiving mail; nothing switches off on the day.

The risk is security. Exchange servers face the internet, hold every mailbox in the organisation and have been a frequent target for attackers in recent years. When an unpatched flaw is published, an unsupported server stays exposed. That is the cause-and-effect at the heart of this deadline: no patches means a growing list of known, unfixed vulnerabilities on your most exposed server.

Compliance is the second effect. Many cyber-insurance policies, audits and industry standards require supported software, so running an unsupported mail server can create problems well before an actual breach.

Does Exchange Server ESU Extend Support Past October 2026?

No. Microsoft offered ESU in two paid periods, and the second one ends in October 2026. Period 1 ran from October 2025 to April 2026. Period 2 covers May to October 2026, must be bought separately through Microsoft volume licensing, and Microsoft has said there will be no extensions after it.

ESU only covers the final builds: Exchange 2016 CU23 and Exchange 2019 CU14 or CU15. If your servers are on an older cumulative update, they were not eligible. Treat ESU as time to finish a migration, not as a way to stay on Exchange 2019.

What Is Exchange Server Subscription Edition (SE)?

Exchange Server SE is the successor to Exchange 2019 and the only on-premises Exchange version Microsoft now supports. It reached general availability on 1 July 2025. Its first build is effectively Exchange 2019 CU15 with a new name and a new licensing model.

Two things change compared with Exchange 2019:

• Servicing: SE follows the Modern Lifecycle Policy. There is no fixed end-of-support date; you stay supported by installing current cumulative updates. Microsoft has committed to giving at least 12 months' notice before support ends.
• Licensing: Microsoft's product terms state that SE server licences and CALs (client access licences) must be subscription licences or licences with active Software Assurance. Perpetual Exchange 2019 licences without Software Assurance do not cover SE.

SE runs on Windows Server 2019, 2022 or 2025, Standard or Datacenter, and Microsoft recommends Server Core. A Windows Server licence is a separate purchase from the Exchange licence. Microsoft's Exchange Server supportability matrix lists the current operating system and .NET requirements.

As for updates: Microsoft said in August 2026 that SE CU1 had been delayed beyond its original 2026 target while it adds the latest security fixes. Check the Exchange Team blog for its status before planning around it.

How Do You Upgrade Exchange 2019 to Exchange Server SE?

If you run Exchange 2019 CU14 or CU15, you can upgrade in place: the SE RTM build installs on top of it like a cumulative update. Here is the general order.

1. Confirm your SE licensing is in place through your volume licensing agreement, with subscription or Software Assurance cover for servers and CALs.
2. Take a full backup of each Exchange server and confirm your mailbox databases are healthy.
3. Check the Exchange 2019 build in the Exchange admin center → Servers. If you are below CU14, install CU15 first.
4. Install the latest security update for your current build, and confirm the Windows Server version and .NET Framework match the supportability matrix.
5. Download the SE RTM installation media through your volume licensing portal.
6. Put the server into maintenance mode, then run Setup from the SE media and choose the upgrade option, exactly as you would install a CU. In a database availability group (DAG), upgrade one member at a time.
7. Take the server out of maintenance mode, test mail flow, Outlook, mobile devices and OWA, then move to the next server.

Because SE does not support in-place upgrades of the underlying operating system between major Windows Server versions, plan any OS change as a new-server build with a mailbox move, not as an in-place Windows upgrade.

Should You Migrate Exchange 2016 to 2019 First?

No, not as a destination. Exchange 2019 is just as unsupported as 2016, so migrating 2016 to 2019 now only adds a step. Exchange 2016 cannot be upgraded in place to SE; it needs a migration.

The usual route is to build new SE servers in the same organisation, move mailboxes and other roles across, then decommission the 2016 servers. Microsoft's system requirements list coexistence with Exchange 2016 as supported when every 2016 server, including Edge Transport servers, runs CU23. Check that page again before each SE update, as coexistence rules can change.

The alternative is Exchange Online. If you no longer want to run mail servers, a hybrid setup lets you move mailboxes to Microsoft 365 and retire on-premises Exchange over time, keeping one server only if you still need it for management.

A Common Mistake We See

The most common oversight is the operating system underneath Exchange. Teams plan the Exchange upgrade carefully, then find their Exchange 2016 or 2019 servers run on Windows Server 2012 R2 or 2016, which SE does not support. In-place Windows upgrades are not supported with Exchange installed, so the server has to be rebuilt anyway.

Plan the SE move together with new Windows Server hosts. A genuine Windows Server 2025 Standard licence is a common base for new Exchange servers; licensing for Windows Server is core-based, and our Hyper-V and Windows Server cost guide explains how Standard and Datacenter differ for virtual machines. If you are installing Windows Server for the first time, our Windows Server 2022 Standard install guide walks through it. Note that we sell Windows Server licences, not Exchange Server licences; Exchange SE is licensed through Microsoft volume licensing.

Frequently Asked Questions

When is Exchange 2019 EOL?

Exchange Server 2019 reached end of life on 14 October 2025. Mainstream support had already ended on 9 January 2024. Paid Extended Security Updates were available for CU14 and CU15 servers, but the final ESU period ends in October 2026 and Microsoft says it will not be extended.

When is Exchange 2016 EOL?

Exchange Server 2016 also reached end of life on 14 October 2025, ten years after its release. Mainstream support ended on 13 October 2020. Only servers on CU23 were eligible for the paid ESU programme, which ends in October 2026.

Is Exchange 2019 CU15 the last update?

Yes. Exchange 2019 CU15, released in February 2025, was the final cumulative update for Exchange 2019. After that, only security updates were released, and those stopped at end of life unless you bought ESU. CU15 is also the recommended starting point for an in-place upgrade to Exchange Server SE.

Can I upgrade Exchange 2016 directly to Exchange SE?

Not in place. Exchange 2016 must be migrated: install Exchange SE on new servers in the same organisation, move mailboxes and services, then decommission the 2016 servers. Every Exchange 2016 server must be on CU23 for coexistence with SE to be supported.

What Exchange 2019 versions can upgrade in place to SE?

Exchange 2019 CU14 and CU15 can upgrade in place. Microsoft says the SE RTM build installs as a cumulative update on either. Servers on older Exchange 2019 builds should be updated to CU15 first, then upgraded to SE.

Does Exchange Server SE need a subscription?

Yes, in licensing terms. Microsoft's product terms require Exchange SE server licences and CALs to be subscription licences or licences with active Software Assurance. Perpetual Exchange 2019 licences without Software Assurance do not give you rights to run SE.

What Windows Server version does Exchange SE need?

Exchange Server SE is supported on Windows Server 2019, 2022 and 2025, Standard or Datacenter, with Server Core recommended. Windows Server is licensed separately from Exchange, so new Exchange hosts need their own Windows Server licence and the required Windows Server CALs.

Conclusion

With the Exchange 2019 EOL date behind us and ESU ending in October 2026, the decision is now between Exchange Server SE on supported Windows Server hosts and a move to Exchange Online. Upgrade 2019 CU14/CU15 in place, migrate 2016 to new servers, and rebuild on a current OS. For the server side, browse our Windows Server licences.

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